B

Ballistic Coefficient -- The calculated aerodynamics (atmospheric resistance) of a bullet after its been fired and before it reaches target -- a mathematical index for deceleration of a projectile in flight.

Balloon Head -- When the primer on a cartridge case extends into the powder chamber – should not be reloaded.

Bearing Surface -- The surface area of a bullet that makes direct contact with the rifling of a barrel (lands and grooves).

Bedding -- The material and/or method for fitting a barrel and action to a rifle stock.

E

Erosion (Throat Erosion) -- The wearing of parts (usually the throat of the barrel) due to extreme heat and friction commonly caused from hot-burning powders, over-firing and / or large capacity loading.

Expanding Bullet -- A bullet that is designed to expand on impact, thus creating a more lethal contact with the target – typical types include hollow points and soft points.

Wind Deflection -- The lateral (side-to-side) effect on a bullet in flight caused by crosswind.

Work Hardened -- The eventual brittleness of a cartridge case due to repeated stress on the metal caused from repeated firing and reloading – typically around the neck of the case resulting in cracking and splitting.